Tissue prosthesis insertion system and method

ABSTRACT

A tissue prosthesis insertion system ( 80 ) includes a first assembly ( 10 ) comprising a plurality of nested tubes ( 12 ), one of the tubes being a carrier tube ( 14 ) which, in use, receives a component ( 16 ) of a tissue prosthesis at a distal end of the carrier tube ( 14 ). A magnetic mount ( 44 ) is carried at a proximal end of the first assembly ( 10 ). A second assembly ( 82 ) is removably attachable to the first assembly ( 10 ). An attachment device ( 92 ) is carried at a distal end of the second assembly ( 82 ), the attachment device ( 92 ) being responsive to the magnetic mount ( 44 ) of the first assembly ( 10 ), the magnetic mount ( 44 ) and the attachment device ( 92 ) carrying complementary engaging formations to facilitate hermetic sealing between the magnetic mount ( 44 ) and the attachment device ( 92 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase application under 35 U.S.C.§371 of International Patent Application No. PCT/AU2007/001657 filed onOct. 31, 2007, the contents of which is incorporated herein by referencein its entirety.

FIELD

This invention relates, generally, to tissue prostheses and, moreparticularly, to a tissue prosthesis insertion system and to a method offorming a tissue prosthesis at a site in a patient's body. While theinvention has particular application in the field of intervertebral discnucleus replacement, the invention can be used in other tissueprosthesis insertion applications.

BACKGROUND

In the delivery of a prosthesis in a minimally invasive manner, use ismade of a working cannula which is inserted through an incision in apatient's skin to the site to facilitate percutaneous delivery of theprosthesis to the site. A delivery mechanism is inserted into a lumen ofthe cannula for delivery of the prosthesis to the site. Generally, thecannula and the delivery mechanism are mounted on some form of structuresuch as a control device, a dispensing arrangement, or the like. Inaddition, the cannula and the delivery mechanism are made as thin aspossible so that the incision is made as small as possible.

In the case of a tissue prosthesis such as an intervertebral discnucleus prosthesis, there is a need to perform an annulotomy on theannulus of the disc to gain access to an interior of the disc. Theworking cannula, after being inserted percutaneously, needs to bealigned with the opening formed in the annulus and retained in suchalignment. It would therefore be advantageous to disturb the position ofthe cannula and the delivery device as little as possible and to keepthe assembly as stable as possible.

SUMMARY

According to a first aspect of the invention, there is provided a tissueprosthesis insertion system which includes

a first assembly comprising a plurality of nested tubes, one of thetubes being a carrier tube which, in use, receives a component of atissue prosthesis at a distal end of the carrier tube;

a magnetic mount carried at a proximal end of the first assembly;

a second assembly removably attachable to the first assembly; and

an attachment device carried at a distal end of the second assembly, theattachment device being responsive to the magnetic mount of the firstassembly, the magnetic mount and the attachment device carryingcomplementary engaging formations to facilitate sealing between themagnetic mount and the attachment device.

The complementary engaging formations of the magnetic mount and theattachment device may comprise a Luer slip fitting. By “Luer slipfitting” is meant that one of the engaging formations comprises atapered socket and the other of the engaging formations comprises atapered fitting receivable in the tapered socket to form a hermetic sealbetween the fitting and the socket.

The magnetic mount of the first assembly may be a first magnetic mountand the attachment device may comprise a second magnetic mount whichmagnetically attaches to the first magnetic mount.

The second assembly may include a stiffening member received within thefirst assembly, the stiffening member, in use, projecting into aninterior of the component of the prosthesis, the stiffening memberhaving a securing formation at its proximal end which engages theengaging formation of the magnetic mount in a sealing manner.

Further, the system may include a withdrawing device attachable to thefirst assembly, the withdrawing device, in use, being in communicationwith the interior of the component of the prosthesis and, with thestiffening member in position, creating a closed system so thatoperating the withdrawing device causes an increase in the volume of theclosed system with a corresponding reduction in the pressure in theinterior of the component, resulting in the component collapsing aboutthe stiffening member.

The withdrawing device may be operable to test the integrity of thefirst assembly with the component mounted on the first assembly.

The first assembly may include a protective sheath, constituting one ofthe tubes of the first assembly, received over the component after ithas been collapsed on to the stiffening member. At least one of theprotective sheath and the component may be treated to facilitate slidingdisplacement between the protective sheath and the component. Thetreating of the protective sheath and/or the component may occur priorto inserting the first assembly into a working cannula used forinsertion of the tissue prosthesis into position at a site in apatient's body. The treating may involve immersing the distal end of thefirst assembly in a lubricating fluid such as water. Instead, thetreating may involve coating an inner surface of the protective sheathwith a hygroscopic material or a hydrophilic material such as, forexample, a hydrogel.

The protective sheath may have a distal end configured to facilitatesliding displacement of the protective sheath relative to the componentof the prosthesis. More particularly, the distal end of the protectivesheath may be configured by being bifurcated.

The protective sheath may include an operating member arranged at itsproximal end to facilitate manipulation of the protective sheath.

The system may include the component, the component comprising anenvelope of an elastically deformable material, the envelope defining anaccess opening with a flow control member being arranged in the accessopening, the flow control member being configured to permit withdrawalof fluid from an interior of the envelope prior to filling the envelopewith a filler material. The flow control member may be a flow controlvalve which, in a rest condition, defines a withdrawal opening to allowwithdrawal of the fluid from the interior of the envelope. The valve maybe a duckbill valve having a pair of opposed operating flaps, the flapsbeing shaped so that, in their rest condition, they are spaced from eachother to define the withdrawal opening.

The second assembly may comprise a filler tube received through thefirst assembly to communicate with the interior of the envelope and afiller material dispenser mountable to a proximal end of the fillertube. The dispenser assembly may feed into a static mixer, a distal endof the static mixer carrying the attachment device, the arrangementbeing such that, when the second assembly is fast with the firstassembly and the withdrawing device is attached to the first assembly, asecond closed system is created which enables fluid to be withdrawn fromthe interior of the envelope by the withdrawing device to create a lowpressure region in the envelope. A “low” pressure is defined as apressure below ambient pressure.

The dispenser may contain filler material, the filler material being ofthe same class or type of material as the material of the envelope sothat, when the envelope has been charged with the filler material andthe filler material has been allowed to set, a tissue prosthesis isformed which is elastically deformable. By “elastically deformable” ismeant that the prosthesis can be deformed by the application of a forceand, upon removal of the force, the tissue prosthesis returns to itsundeformed state.

The system may include an obturating device receivable in one of thetubes of the first assembly for tamping a part of the tissue prosthesisinto position after formation of the tissue prosthesis.

The obturating device may carry a locking member at its proximal end forlocking to a working cannula of the system so that, after tamping of thepart of the tissue prosthesis, the working cannula and the obturator canbe removed simultaneously.

According to a second aspect of the invention, there is provided atissue prosthesis insertion system which includes

an assembly comprising a plurality of nested tubes, one of which is acarrier tube for carrying a component of a tissue prosthesis at itsdistal end and another of which is a filler tube received with clearancein the carrier tube to define a passage between the filler tube and thecarrier tube, the proximal end of the filler tube and the proximal endof the carrier tube being in sealing engagement; and

a withdrawing device attachable to the assembly so that, when thewithdrawing device is attached and the component of the tissueprosthesis is mounted on the distal end of the carrier tube, a closedsystem is formed which allows the withdrawing device to be used toincrease the volume of the closed system to form a low pressure regionat least in the component.

The assembly may comprise a stiffening member received in the carriertube, a proximal end of the stiffening member and a proximal end of theassembly carrying complementary engaging formations for enabling thestiffening member to engage sealingly with at least one of the pluralityof nested tubes to create an initial closed system, operation of thewithdrawing device forming a low pressure region in the interior of thecomponent, in use, to cause the component to collapse around thestiffening member. The system may include a filler tube insertable intothe carrier tube after removal of the stiffening member to contribute tothe formation of a further closed system which is then acted on by thewithdrawing device to increase the volume of the closed system to reducethe pressure in the interior of the component.

The withdrawing device may be operable to test the integrity of thesystem to ensure that there are no leaks in the system.

According to a third aspect of the invention, there is provided a tissueprosthesis insertion system which includes

a working cannula for accessing a site in a patient's bodypercutaneously in a minimally invasive manner for carrying out a tissueprosthesis insertion procedure at the site; and

an obturating device receivable in the cannula for tamping a part of atissue prosthesis into position after formation of the tissueprosthesis.

The obturating device may comprise a blunt-ended rod slidably receivablein the working cannula.

According to a fourth aspect of the invention, there is provided atissue prosthesis component which includes

an envelope of an elastically deformable material, the envelope definingan access opening; and

a flow control member arranged in the access opening, the flow controlmember being configured to permit withdrawal of fluid from an interiorof the envelope prior to filling the envelope with a filler material.

The flow control member may be a flow control valve which, in a restcondition, defines a withdrawal opening to allow the passage of fluid inboth directions. The envelope may have a neck portion, the neck portiondefining the access opening and the flow control member being arrangedwithin the neck portion.

According to a fifth aspect of the invention, there is provided a methodof preparing a first assembly of a tissue prosthesis system forinsertion into a patient's body, the method comprising

providing the first assembly which comprises a plurality of nestedtubes, one of the tubes being a carrier tube;

mounting a component of the prosthesis on a distal end of the carriertube, the component being of an elastically deformable material;

inserting a stiffening member into the first assembly so that thestiffening member extends into an interior of the component and causinga proximal end of the stiffening member to sealingly engage a proximalend of the first assembly;

attaching a withdrawing device to the first assembly so that thewithdrawing device is in fluid communication with the interior of thecomponent; and

operating the withdrawing device to reduce the pressure in the interiorof the component to cause the component to collapse about the stiffeningmember.

The method may include attaching the withdrawing device to a fluid portof the first assembly in a sealing manner. The withdrawing device may bea syringe which is attached by a Luer lock mechanism to the fluid portof the first assembly.

After the component has been collapsed about the stiffening member, themethod may include placing a protective sheath about the component. Moreparticularly, the method may include placing the protective sheath aboutthe component by sliding the protective sheath over the component, theprotective sheath constituting one of the tubes of the nested tubes ofthe first assembly.

Further, the method may include treating one of the protective sheathand the component with a lubricating medium to facilitate relativedisplacement between the protective sheath and the component.

The method may include using the withdrawing device to test theintegrity of the combination of the first assembly and the component andthe stiffening member attached to the first assembly.

According to a sixth aspect of the invention, there is provided a methodof forming a tissue prosthesis at a site in a patient's body, the methodincluding

providing a first assembly comprising a plurality of nested tubes, oneof the tubes being a carrier tube with a component of the prosthesiscarried at a distal end of the carrier tube;

inserting the first assembly into a cannula placed in the patient'sbody;

magnetically attaching a second assembly to a proximal end of the firstassembly; and

charging a filler material from the second assembly into the componentand allowing the filler material to set.

The method may include, initially, preparing the first assembly asdescribed above.

The method may include, once the distal end of the first assembly is atthe desired location at the site in the patient's body, withdrawing theprotective sheath to expose the component, the component being anenvelope of an elastically deformable material.

The method may include removing the stiffening rod prior to magneticallyattaching the second assembly to the first assembly. Further, the methodmay include causing the second assembly to engage sealingly with thefirst assembly so that, together with the component and the withdrawingdevice, a closed system is formed.

After the second assembly has been attached to the first assembly, themethod may include operating the withdrawing device to create a lowpressure in the component. Further, the method may include using thewithdrawing device to test the integrity of the system comprising thetwo assemblies and the component attached to the first assembly.

The method may include dispensing the filler material from a dispenserof the second assembly. Preferably, the method includes purging fillermaterial from the dispenser prior to attaching the dispenser to a staticmixer constituting a part of the second assembly. The method mayinclude, during filling of the component via a filler tube extendingfrom the static mixer, operating the withdrawing device at least tomaintain, or increase, the volume of the closed system.

The method may include, after filling the component, detaching thecarrier tube from the tissue prosthesis formed by the combination of thecomponent and the filler material contained in the component. Thecarrier tube may be detached prior to the filler material having curedor set or after the filler material has at least partially set. Themethod may include detaching the carrier tube from the tissue prosthesiswhen the required pressure has been reached in the component. In thecase of an intervertebral disc nucleus prosthesis, the required pressuremay be that which inhibits distraction of the disc.

In an embodiment, the method may include detaching the tissue prosthesisby relative axial motion between the carrier tube and a displacementdevice of the first assembly. The displacement device may be a furthertube arranged about the carrier tube and the relative axial motion maybe effected by withdrawing the carrier tube relative to the displacementdevice. In another embodiment, the method may include detaching thetissue prosthesis by filling the component with filler material to theextent that the component is released from the carrier tube. In afurther embodiment, the method may include detaching the tissueprosthesis by manipulating the carrier tube relative to the component tocause separation of a part of the component attached to the carrier tubefrom a remainder of the component, the separation occurring at a zone ofweakness in the component. The manipulation may involve rotating thecarrier tube with respect to the component.

The method may include, after formation of the tissue prosthesis,tamping a part of the tissue prosthesis into position.

If necessary or desirable, the method may include, before placing thecomponent in position at the site, preparing the site. The method mayinclude preparing the site by removing degenerative tissue from the siteprior to placing the component at the site.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a plan view of a first assembly of a tissue prosthesisinsertion system in accordance with an embodiment of the invention;

FIG. 2 shows a sectional side view of the first assembly of the systemof FIG. 1 taken along line II-II in FIG. 1;

FIG. 3 shows a sectional side view, on an enlarged scale, of the part ofthe first assembly surrounded by circle ‘A’ in FIG. 2;

FIG. 4 shows a sectional side view, on an enlarged scale, of the part ofthe first assembly surrounded by circle ‘B’ in FIG. 2;

FIG. 5 shows a plan view of an assembly of the tissue prosthesisinsertion system;

FIG. 6 shows a sectional side view of the assembly of the system takenalong line VI-VI in FIG. 5;

FIG. 7 shows a sectional side view, on an enlarged scale, of the part ofthe assembly surrounded by circle ‘C’ in FIG. 6;

FIG. 8 shows a sectional side view, on an enlarged scale, of the part ofthe assembly surrounded by circle ‘D’ in FIG. 6;

FIG. 9 shows a plan view of a valve member forming part of a tissueprosthesis of the system;

FIG. 10 shows an end view of the valve member;

FIG. 11 shows a sectional side view of the valve member taken along lineXI-XI in FIG. 10;

FIG. 12 shows a schematic side view of a working cannula of the assemblyin position after formation of the tissue prosthesis; and

FIG. 13 shows a schematic side view of a further part of the systeminserted into the cannula to complete formation of the tissueprosthesis.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring initially to FIGS. 1-4 of the drawings, a first assembly of atissue prosthesis insertion system is illustrated and is designatedgenerally by the reference numeral 10. The first assembly 10 comprises aplurality of nested tubes 12. As shown more clearly in FIG. 4 or thedrawings, the set of nested tubes 12 comprises an inner, carrier tube 14on which a component, in the form of an envelope, 16 of a tissueprosthesis is mounted, the component 16 being mounted on a distal end ofthe carrier tube 14. The carrier tube 14 is received within a push-offtube 18 which is used for removing the envelope 16, after filling, fromthe carrier tube 14 as will be described in greater detail below.

The nested tubes 12 further include a protective sheath 20, arrangedabout the push-off tube 18. As illustrated most clearly in FIGS. 2 and 4of the drawings, the protective sheath 20 is of a length to cover theenvelope 16, the sheath 20 projecting beyond a distal end of theenvelope 16 when in its operative, protective position. It is to benoted that the nested tubes 12 are shown, in use, mounted in a workingcannula 22 used for inserting the first assembly 10 percutaneously todeliver the envelope 16 into a site at a patient's body in which theprosthesis is to be formed.

The nested tubes 12 are all of a metal material such as a steel materialwhich is bio-compatible.

The first assembly 10 further includes a stiffening member in the formof a stiffening rod 24. The stiffening rod 24 is of a length to projectfrom a proximal end of the first assembly 10 through a lumen 26 (FIG. 4)of the carrier tube 14 to be received in an interior 28 of the envelope16.

A collar assembly 30 is arranged at a proximal end of the nested tubes12. The collar assembly 30 comprises a first collar 32 secured to aproximal end of the cannula 22. The cannula 22 has a pair ofdiametrically opposed, longitudinally extending slits, one of which isshown at 34 in FIG. 1 of the drawings, arranged distally of the collar32. The protective sheath 20 is slidably arranged relative to thecannula 22 and has a pair of opposed, radially outwardly extending tabs38 arranged at its proximal end. The tabs 38 project through the slits34 in the cannula 22 to enable a clinician to manipulate the protectivesheath 20.

The push-off tube 18 has a collar 36 arranged at its proximal end, thecollar 36 being connected to the collar 32 of the cannula 22 via abayonet fitting.

The carrier tube 14 carries a Y-connector 42 at its proximal end, theY-connector 42 extending from a collar 40. The collar 40 attaches to thecollar 36 of the push-off tube 18. The Y-connector 42 carriers amagnetic mount 44 at its proximal end. The magnetic mount 44 carries aplurality of annular magnets 46. These magnets 46 are rare earth magnetsand are covered by a cover member 48.

The Y-connector 42 further includes a branch limb 50 defining aconnection port 52 for a withdrawing device. The connection port 52 isin communication with a passage (not shown) defined between the carriertube 14 and, initially, the stiffening rod 24.

The stiffening rod 24 carries a securing formation in the form of amount 54 at its proximal end. A distal part 56 of the mount 54 istapered and engages a tapered socket 58 defined by the magnetic mount 44in a hermetically sealing manner so that, once a withdrawing device hasbeen attached to the port 52, a closed system is formed.

More particularly, once the envelope 16 has been attached to the distalend of the carrier tube 14, the stiffening rod 24 is inserted throughthe lumen 26 of the carrier tube 14 to be received in the interior 28 ofthe envelope 16. When the distal end of the stiffening rod 24 isreceived in the envelope 16, the distal part 56 of the mount 54 of thestiffening rod 24 sealingly engages with the socket 58 in the magneticmount 44 of the Y-connector 42 to form a hermetic seal.

A withdrawing device in the form of a syringe 62 (FIG. 6) is connectedvia a Luer fitting 64 to the port 52 of the Y-connector 42 to form aclosed system. A plunger 66 of the syringe 62 is drawn in the directionof arrow 68. This increases the volume of the closed system, reducingthe pressure in the interior 28 of the envelope 16 and causing theenvelope 16 to collapse about the distal end of the stiffening rod 24.

The tabs 38 of the protective sheath 20 are gripped by an operatorassembling the first assembly 10 and are urged in the direction of arrow70 (FIG. 2) to cause the protective sheath 20 to slide over and protectthe envelope 16. To facilitate sliding movement between the protectivesheath 20 and the envelope 16, a distal end of the first assembly 10 canbe immersed in a suitable lubricating medium such as, for example,water. In this regard it should be noted that the envelope 16 is made ofsilicone material rendering it hydrophobic. Thus, the water acts as alubricant and enables the protective sheath 20 to be slid over theenvelope 16. Instead of immersing the distal end of the first assembly10 in the lubricating medium, an internal surface of the protectivesheath 20 could, optionally, be coated with a lubricating medium of ahygroscopic or hydrophilic material such as a hydrogel.

After retracting the sheath 20 in the direction opposite to that ofarrow 70, the integrity of the first assembly 10 is tested for leaks byfurther withdrawing the plunger 66 of the syringe 62 in the direction ofarrow 68. If the plunger 66 does not return to its previous position,this is an indication that there is a leak in the first assembly 10 andremedial action can be taken to locate the leak. Conversely, should theplunger 66 return to its previous position, this is an indication thatthe integrity of the first assembly 10 is intact and the procedure canproceed.

Instead of pulling on the plunger 66 of the syringe 62, testing of theintegrity of the first assembly 10 could involve pushing on the plunger66 of the syringe 62 and then releasing the plunger 66. If the plunger66 does not return to its original position that is an indication thatthere is a leak in the system such as may occur if the envelope 16 istorn.

Referring now to FIGS. 5-8 of the drawings, a tissue prosthesisinsertion system is shown in greater detail and is designated generallyby the reference numeral 80. The system 80 includes the first assembly10 and a second assembly 82. The second assembly 82 comprises a fillertube 84 including a static mixer 86 at a proximal end of the filler tube84. The static mixer 86 is secured to a distal end of a filler materialdispenser 88. The filler material dispenser 88 has a screw-threadedattachment 89 for engaging a screw-threaded boss 90 at a proximal end ofthe static mixer 86.

A distal end of the static mixer 86 carries an attachment device in theform of a second magnetic mount 92. As illustrated more clearly in FIG.7 of the drawings, the magnetic mount 92 comprises a pair of annularrare earth magnets 94 closed off by a cover 96. The mount 92 alsoincludes a tapered fitting 98. The tapered fitting 98 of the mount 92and the tapered socket 58 of the mount 44 define complementary engagingformations. Thus, the tapered fitting 98 is received within the socket58 of the magnetic mount 44 of the Y-connector 42 in a hermeticallysealing manner, the fitting 98 and the socket 58 constituting a Luerslip fitting. Thus, once again, once the syringe 62 has been attached tothe port 52 of the Y-connector 42, a closed system is formed.

The benefit of magnetically attaching the second assembly 82 to thefirst assembly 10 is that the requirement for relative rotation betweenthe two assemblies 10 and 82 for attachment to each other is obviated.This also enables the cannula 22 of the first assembly 10 moreaccurately to be retained in position, in use. It also maintains theengagement of the two assemblies 10 and 82 during filling of theenvelope 16 as will be discussed in greater detail below.

The filler material used for forming the tissue prosthesis is a siliconerubber material. To inhibit curing of the filler material prior to itsbeing charged into the envelope 16, the filler material is retained intwo, separate parts. For this purpose, the dispenser 88 includes twoseparate reservoirs 100, in each of which one part of the fillermaterial is initially received. Each reservoir 100 has a plunger (notshown) associated with it for dispensing the parts of the fillermaterial simultaneously from the reservoirs 100 into the static mixer 86where the parts are mixed prior to being charged into the filler tube 84to be injected into the interior 28 of the envelope 16. The plungers aredisplaceable together with each other via a suitable displacing device(also not shown), for example, a pneumatic gun.

After removal of the stiffening rod 24, the second assembly 82 isattached to the first assembly 10 via the magnetic mounts 44 and 92.More particularly, the part of the second assembly 82 comprising thestatic mixer 86 with the filler tube 84 projecting from the static mixer86 is magnetically attached to the first assembly 10 via the magneticmounts 44 and 92 with the fitting 98 sealingly engaging in the socket58. Prior to attaching the dispenser 88 to the static mixer 86, fillermaterial is purged from the reservoirs 100 by urging the plungerstowards the threaded end 89 of the dispenser 88 to expel a portion offiller material from the reservoirs 100 to ensure that the correct ratioof the two parts of the filler material is dispensed. The dispenser 88is then attached to the static mixer 86.

The pressure in the interior 28 of the envelope 16 is again lowered bywithdrawing the plunger 66 of the syringe 62 in the direction of arrows68. This serves to collapse the envelope 16 prior to the filler materialbeing charged via the filler tube 84 into the interior 28 of theenvelope 16. To enable the pressure in the interior 28 of the envelope16 to be lowered, the filler tube 84 is a loose fit within the carriertube 14 to create an annular passage 102 (FIG. 8) via which air can bewithdrawn from the interior 28 of the envelope 16 by the syringe 62.

After lowering the pressure in the interior of the envelope 16, theintegrity of the system 80 is again checked by further attempting towithdraw the plunger 66 from the syringe 62 in the direction of thearrows 68. Should the plunger 66 remain in its withdrawn position, thisis an indication that there is a leak in the system and remedial actioncan be taken to locate the leak. Conversely, should the plunger 66return to its previous position, this is an indication that theintegrity of the system 80 is intact and the clinician can proceed. Onceagain, instead of pulling the plunger 66, testing could involve pushingthe plunger 66 and determining whether or not it returns to its originalposition. If not, that is an indication that there is a leak in thesystem 80 and remedial action can be taken to locate the leak.

The use of the system 80 will be described with reference to itsapplication in the formation of an intervertebral disc nucleusprosthesis. An intervertebral disc 124 (FIGS. 12 & 13) comprises anannular part called the annulus fibrosis, or annulus, 126. The annulus126 surrounds a nucleus pulposus (not shown). The intervertebral disc124 cooperates with end plates of vertebrae 128 between which the disc124 is sandwiched. When the disc 124 degenerates, there is a tendencyfor nuclear material to extrude through the annulus 126 reducing theefficacy of the disc 124. Should the degeneration be detected at asufficiently early stage, the disc 124 can be restored by replacing thenatural nucleus pulposus with a prosthetic disc nucleus 130.

The applicant has developed a synthetic disc nucleus comprising anenvelope 16 of a silicone material with a filler material of a similarsilicone material. When the filler material has been injected into theenvelope 16 and it has been allowed to set, a uniform, integralstructure is formed which at least partially restores the biomechanicsof the disc. More particularly, the nucleus prosthesis is elasticallydeformable. Thus, the application of force will cause the nucleusprosthesis to deform elastically so that, once the force has beenremoved, the prosthesis will return to its relaxed, undeformed state.The prosthesis is described in greater detail in the applicant'sInternational Patent Application No. PCT/AU2006/001176 entitled “Atissue prosthesis and a method of, and equipment for, forming a tissueprosthesis” filed on 15 Aug. 2006. The contents of that InternationalPatent Application are incorporated by reference in this specificationin their entirety.

To insert the nucleus prosthesis into the disc, an incision in made inthe patient's skin and an annulotomy is performed on the annulus 126 ofthe disc 124 in a minimally invasive manner to form an opening 132. Thisenables access to be gained to the interior of the disc 124. To performthe annulotomy, the cannula 22 is inserted through the incision until adistal ends abuts the annulus 126. An annulotomy performing tool, suchas a trocar or a guide wire plus dilator (not shown), is insertedthrough the cannula 22 and pierces the annulus 126 to enable access tobe gained to the nuclear material of the disc 124. If necessary, anucleotomy is performed to remove the nuclear material. However, incertain circumstances, the degenerative process may have dehydrated,extruded or shrunken the nuclear material so that a cavity has alreadybeen formed and the necessity to perform the nucleotomy is obviated.

Whether or not a nucleotomy is performed, once the cavity in the disc124 is present, the first assembly 10 is inserted into the cannula 22.As indicated above, the first assembly 10 comprises the carrier tube 14with the envelope 16 mounted on a distal end of the carrier tube 14, thepush-off tube 18 and the protective sheath 20, with the protectivesheath 20 extending over the envelope 16.

Once the envelope 16 is in position within the disc 124, the protectivesheath 20 is withdrawn by urging the tabs 38 of the protective sheath 20in the direction opposite to that of the arrow 70, the tabs 38 beingreceived within recesses 104 of the collar 32 of the cannula 22.

The assembly 10 is locked in position relative to the working cannula 22by the bayonet fitting of the collar 36 of the push-off tube 18 engagingthe collar 32 of the cannula 22.

The stiffening rod 24 is removed and the second assembly 82 is attachedto the first assembly 10, as previously described. Some filler materialis purged from the reservoirs 100 of the dispenser 88 and the dispenser88 is then attached to the proximal end of the static mixer 86. Thisre-forms the closed system enabling air to be removed from the envelope16 by operating the syringe 62 and pulling its plunger 66 in thedirection of arrows 68.

The plungers of the dispenser 88 are then urged towards the distal endof the dispenser 88 to discharge material from the reservoirs 100. Theparts of the filler material discharged from the reservoir 100 are mixedtogether in the static mixer 86 before being fed into the filler tube84. The plunger 66 of the syringe 62 is continued to be withdrawn in thedirection of arrow 68 during passage of the filler material along thefiller tube 84 at least to maintain or to increase the volume of theclosed system to remove air from the envelope 16 as the filler materialis charged into the envelope 16. The filler material 84 is conveyedthrough the filler tube 84 into the interior 28 of the envelope 16through a tissue prosthesis component in the form of a filler valve 106.The filler valve 106 will be described in greater detail below.

As the filler material enters the interior 28 of the envelope 16, itcauses the envelope 16 to expand to conform to the shape of the cavitywithin the intervertebral disc. It will be appreciated that, due to theresilient flexibility of the envelope 16, the envelope 16 will readilyconform to the shape of the cavity and the envelope 16 need not be ofany pre-configured dimensions.

Referring now to FIGS. 9-11 of the drawings, the tissue prosthesiscomponent in the form of the filler valve 106 of the envelope 16 isdescribed in greater detail. It is to be noted that the envelope 16 hasa bulbous body portion 108 (FIG. 8) integrally formed with a neckportion 110. The envelope 16 is attached to the distal end of thecarrier tube 14 via the neck portion 110. The valve 106 is receivedwithin the neck portion 110 of the envelope 16. The valve 106 is a duckbill valve having a pair of opposed operating members or operating flaps112. The operating flaps 112, when in their rest condition, as shown inFIGS. 9-11 of the drawings, do not close fully and a slit 114 is definedbetween the operating flaps 112 of the valve 106. This is desirable sothat, prior to filler material being charged into the interior 28 of theenvelope 16, air can be withdrawn from the interior 28 of the envelope16 via the slit 114 using the syringe 62.

Once the filler material has filled the interior 28 of the envelope 16,it occludes the slit 114 or, instead, presses down on the operatingflaps 112 to cause them to deform to close the slit 114. Also, thefiller material could have sufficient viscosity to inhibit extrusion ofthe filler material outwardly through the slit 114. It will beappreciated that, once the filler material has set, it no longer matterswhether or not the slit 114 is fully closed.

To inhibit overfilling of the envelope 16, the envelope is mounted onthe carrier tube 14 such that as the envelope 16 fills with fillermaterial, any excess filler material will “extrude” between the neckportion 110 of the envelope 16 and the carrier tube 14 causing theenvelope 16 to be released from the carrier tube 14.

After the desired quantity of filler material has been charged into theenvelope 16, the second assembly 82 is detached from the first assembly10 by breaking the magnetic bond between the magnetic mounts 44 and 92.The filler tube 84 is withdrawn from the interior of the carrier tube14.

The envelope 16 is detached from the carrier tube 14 by relativedisplacement between the carrier tube 14 and the push-off tube 18. Moreparticularly, the carrier tube 14 is withdrawn from the push-off tube 18by detaching the collar 40 of the Y-connector 42 from the collar 36 ofthe push-off tube 18 and withdrawing the carrier tube 14. This causesthe proximal end of the neck portion 110 of the envelope 16 to come intoabutment with the distal end of the push-off tube 18 causing detachmentof the envelope 16 from the carrier tube 14. The push-off tube 18 isthen removed. The tissue prosthesis 134 (FIGS. 12 & 13), comprising theenvelope 16 filled with the filler material, is retained in positionwithin the intervertebral disc 124 of the patient.

As shown in greater detail in FIGS. 12 and 13 of the drawings, afterremoval of the carrier tube 14, at least a part of the neck portion 110of the envelope 16 may protrude through the annulus 126 of theintervertebral disc 124. In addition a residue of filler material may bepresent in the distal end of the working cannula 22. Therefore, prior toremoval of the working cannula 22, an obturator 136 is inserted into alumen 138 of the cannula 22. The obturator 136 comprises a blunt-endedrod 140 which is a tight fit within the lumen 138 of the cannula 22.

The obturator 136 is used to urge any residue of filler material intothe disc cavity and to tamp the part of the neck portion 110 of theenvelope 16 into the disc cavity, as shown in FIG. 13 of the drawings.The prosthesis 134 is thus entirely contained within the disc cavity 134with minimal, if any, protrusion into the annulus 126 of the disc 124.

The obturator 136 can, if desired, be locked to the working cannula 22by an attachment collar 142 carried at a proximal end of the obturator136 locking to the collar 32 of the working cannula 22 in a bayonetfitting manner. This allows the obturator 136 to be retained in positionduring setting of the filler material and inhibits extrusion of fillermaterial from the envelope 16 and/or from the disc cavity.

After completion of the tamping and setting process, the working cannula22 and the obturator 136 are removed.

Tamping the neck portion 110 of the envelope 16 into the disc cavity 122inhibits prosthesis expulsion and excessive loading on the aperture 132in the annulus 126 of the disc 124. In addition, the fact that there isno remnant of the envelope 16 in the annulus 124 enhances closure of theaperture 132 in the annulus 124.

It is an advantage of the invention that a tissue prosthesis insertionsystem is provided which is simple to operate by a clinician. Theassemblies are easily connected together using the magnetic connectionwhich improves the stability of the device and obviates the need forrelative rotation of the assemblies relative to one another to connectthem together. In addition, the use of the protective sheath protectsthe envelope against damage while it is being inserted into andpositioned in the patient's body. The sheath is relatively simple tooperate by the clinician thereby improving the performance of the systemas a whole. Further, the use of the syringe as a low pressure generatingdevice simplifies the system and precludes the need for complicatedpumps, etc. Also, due to the fact that the syringe provides a closedsystem, it is not necessary to continuously withdraw air out of theenvelope while it is being charged with filler material. This furthersimplifies operation of the system.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

The invention claimed is:
 1. A tissue prosthesis insertion system,comprising: a first assembly including: a plurality of nested tubes, oneof the tubes being a carrier tube which, in use, receives a component ofa tissue prosthesis at a distal end of the carrier tube; a firstmagnetic mount carried at a proximal end of the first assembly; saidfirst magnetic mount having a set of annular magnets and a taperedsocket; a second assembly removably attachable to the first assemblywhich, in use, facilitates the delivery of filler material to thecomponent; said second assembly including: a second magnetic mountcarried at a distal end of the second assembly; said second magneticmount having another set of annular magnets and a tapered fittingdimensioned to be received with said tapered socket in a hermeticallysealing manner sealing said first assembly to said second assembly; saidset of annular magnets and said another set of annular magnets beingarranged relative to one another to help maintain coupling engagementbetween said first assembly and said second assembly and tosubstantially prevent rotational movement between said first assemblyand said second assembly during disengagement from one another; aworking cannula having a pair of diametrically opposed longitudinallyextending cannula slits, said working cannula being dimensioned forreceiving therein said plurality of nested tubes to facilitate thepercutaneous delivery of the component to an implant site in the body ofa patient; wherein said plurality of nested tubes further includes apush off tube dimensioned for receiving therein said carrier tube, saidpush off tube having arranged thereabout a protective sheath with asufficient length to cover and project beyond a distal end of thecomponent when in an operative position for delivery to the implantsite; and wherein said tapered fitting and said tapered socket define aLuer slip fitting.
 2. The system of claim 1, further comprising: acollar assembly forming part of said first assembly and arranged at aproximal end of said first assembly, said collar assembly including: acannula collar disposed distally of said cannula slits and secured to aproximal end of said working cannula; a push-off tube collar arranged ata proximal end of said push-off tube, said push-off tube collarincluding a bayonet fitting to facilitate connecting said push-off tubecollar to said cannula collar; and a carrier tube collar coupled to saidpush-off tube collar.
 3. The system of claim 2, further comprising: astiffening rod forming part of said first assembly, said stiffing rodhaving a sufficient length to protect from a proximal end of said firstassembly through a lumen forming part of said carrier tube and into aninterior space of the component when disposed on the distal end of saidcarrier tube; a Y-connector disposed at a proximal end of said carriertube, said Y-connector having a distal end and a proximal end forcarrying said first magnetic mount; said Y-connector including a branchlimb with a fluid connection port for facilitating the removableattachment thereto of a fluid withdrawing device, said branch limb beingin fluid communication with an initial passageway defined between saidcarrier tube and said stiffing rod; and a stiffening rod tapered mountdisposed at about a proximal end of said stiffening rod, said stiffeningrod tapered mount being dimensioned to be received within said taperedsocket forming part of said first magnetic mount to form a hermeticalseal therebetween so that once the withdrawing device is coupled to saidconnection port a closed system is formed wherein a distal part of saidstiffening rod tapered mount sealing engages with said tapered socket insaid first magnetic mount to form a hermetic seal.
 4. The system ofclaim 3 wherein said second assembly further including: a filler tubehaving a distal end and a proximal end, said filler tube receivedthrough the first assembly to communicate with an interior of thecomponent, in use; a static mixer mountable to the proximal end of saidfiller tube; said static mixer having a distal end and a proximal end,said distal end carrying said second magnetic mount and said proximalend carrying a screw-threaded boss; and a filler material dispenserhaving a distal end screw-threaded attachment secured to a distal endthereof, said screw-threaded attachment being dimensioned to be securedremovably to said screw-threaded boss to facilitate securing said fillermaterial dispenser to said static mixer.
 5. The system of claim 4 whichincludes a withdrawing device attachable to the first assembly, thewithdrawing device, in use, being in communication with the interior ofthe component of the prosthesis and, with the filler tube in position,creating a closed system so that operating the withdrawing device causesan increase in the volume of the closed system.
 6. The system of claim5, wherein when the second assembly is coupled with the first assemblyand the withdrawing device is attached to the first assembly, a secondclosed system is created which enables fluid to be withdrawn from theinterior of the component by the withdrawing device to create a lowpressure region in the component.
 7. The system of claim 6 in which thedispenser contains filler material, the filler material being of thesame class of material as the material of the envelope so that, when theenvelope has been charged with the filler material and the fillermaterial has been allowed to set, a tissue prosthesis is formed which iselastically deformable.
 8. The system of claim 3, wherein thewithdrawing device, in use, being in communication with the interior ofthe component of the prosthesis and, with the stiffening rod taperedmounted in sealing position with said tapered socket, creating a closedsystem so that operating the withdrawing device causes an increase inthe volume of the dosed system with a corresponding reduction in thepressure in the interior of the component, resulting in the componentcollapsing about the stiffening rod.
 9. The system of claim 8, whereinsaid plurality of nested tubes includes said protective sheath, andwherein said protective sheath is received over the component after ithas been collapsed on to the stiffening rod.
 10. The system of claim 9in which at least one of the protective sheath and the component istreated to facilitate sliding displacement between the protective sheathand the component.
 11. The system of claim 9 in which the protectivesheath has a distal end configured to facilitate sliding displacement ofthe protective sheath relative to the component of the prosthesis. 12.The system of claim 9, wherein said protective sheath is slidablyarranged relative to said working cannula; and wherein the protectivesheath includes a pair of opposed, radially outwardly extending tabsarranged at its proximal end, said tabs being dimensioned to projectthrough said cannula slits a sufficient distance to facilitatemanipulation of the protective sheath; wherein when said pair of tabsare manipulated in one direction along said cannula slits the protectivesheath slides over and protects the component; and wherein when saidpair of tabs are manipulated in an opposite direction along said cannulaslits the protective sheath retracts and is removed from protecting thecomponent to facilitate integrity testing of said first assembly forfluid leaks.
 13. The system of claim 9 further comprising: an obturatingdevice receivable in one of the tubes of the first assembly for tampinga part of the tissue prosthesis into position after formation of thetissue prosthesis.
 14. The system of claim 8 which includes thecomponent, the component comprising an envelope of an elasticallydeformable material, the envelope defining an access opening with a flowcontrol member being arranged in the access opening, the flow controlmember being configured to permit withdrawal of fluid from an interiorof the envelope prior to filling the envelope with a filler material.15. The system of claim 14 in which the flow control member is a flowcontrol valve which, in a rest condition, defines a withdrawal openingto allow withdrawal of the fluid from the interior of the envelope. 16.The system of claim 8 in which the withdrawing device is operable totest the integrity of the first assembly with the component mounted onthe first assembly; and wherein the withdrawing device is a syringeconnected via a Luer slip fitting to the fluid connection port of saidY-connector.
 17. A method of forming a tissue prosthesis at an implantsite defined by an intervertebral disc cavity, the method comprising thesteps of: inserting a working cannula percutaneously through an incisionand into retention alignment with an annulus opening at the implant siteto provide access to the intervertebral disc cavity; sliding a firstassembly within said cannula as sufficient distance to deliver acomponent of a tissue prosthesis into the intervertebral disc cavity;said first assembly including: a plurality of nested tubes, one of thetubes being a carrier tube with the component of the prosthesis carriedat a distal end of the carrier tube; and a first magnetic mount carriedat a proximal end of the first assembly, said magnetic mount having aset of annular magnets and a tapered socket; magnetically attaching asecond assembly to a proximal end of the first assembly; said secondassembly including: a second magnetic mount carried at a distal end ofthe second assembly, said second magnetic mount having another set ofannular magnets and a tapered fitting dimensioned to be received withsaid tapered socket in a hermetically sealing manner sealing said firstassembly to said second assembly; said set of annular magnets and saidanother set of annular magnets being arranged relative to one another tohelp maintain coupling engagement between said first assembly and saidsecond assembly and to substantially prevent rotational movement betweensaid first assembly and said second assembly during disengagement fromone another; a working cannula having a pair of diametrically opposedlongitudinally extending cannula slits, said working cannula beingdimensioned for receiving therein said plurality of nested tubes tofacilitate the percutaneous delivery of the component to an implant sitein the body of a patient; wherein said plurality of nested tubes furtherincludes a push off tube dimensioned for receiving therein said carriertube, said push off tube having arranged thereabout a protective sheathwith a sufficient length to cover and project beyond a distal end of thecomponent when in an operative position for delivery to the implantsite; and wherein said tapered fitting and said tapered socket define aLuer slip fitting and charging a filler material from the secondassembly into the component and allowing the filler material to set. 18.The method of claim 17 which includes, before placing the component inposition at the site, preparing the site.
 19. The method of claim 18which includes preparing the site by removing tissue from the site priorto placing the component at the site.
 20. The method of claim 17 whichincludes, after filling the component, detaching the carrier tube fromthe tissue prosthesis formed by the combination of the component and thefiller material contained in the component.
 21. The method of claim 20which includes detaching the carrier tube from the tissue prosthesiswhen the required pressure has been reached in the component.
 22. Themethod of claim 20 which includes detaching the tissue prosthesis byrelative axial motion between the carrier tube and a displacement deviceof the first assembly.
 23. The method of claim 20 which includesdetaching the tissue prosthesis by filling the component with fillermaterial to the extent that the component is released from the carriertube.
 24. The method of claim 20 which includes detaching the tissueprosthesis by manipulating the carrier tube relative to the component tocause separation of a part of the component attached to the carrier tubefrom a remainder of the component, the separation occurring at a zone ofweakness in the component.
 25. The method of claim 17 which includes,after formation of the tissue prosthesis, tamping a part of the tissueprosthesis into position.